Bipropellants



United States PatentO 6c BIPROPELLANTS l James N. Short, Borger, Te'x., and ClevelandR. Scott,

Bartlesville, kla., assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application my 3, 1954 1, Serial No. 427,372

"iiciaims. c1. sip-35.4

This invention relates to hypergolic fuels. In.one aspect this invention relates to materials, which when mixed with an oxidizer, exhibit hypergolic properties. In another aspect this invention relates to phosphonic. diamides as hypergolic fuels. In another aspect this invention relates to polymers of phosphonic diamides as;

hypergolic fuels. In anotheraspect this invention relates"to'bipropellants wherein a. phosphonicfdiamide .or a polymer of a, phosphonic diamide is an ingredient. In' 'still another aspect this invention relates to bipropellants' having a phosphonic diamide, or a polymer.

thereof, diluted with a non-hypergolic hydrocarbon, as an ingredient of'said bipropellant. In still another aspect this invention relates to employing the compounds of the invention to develop thrust.

Various materials and combinations of materials have been 'found to be useful as rocket propellants and as propellants in jet propulsion systems. Some propellants consistof a single materiahand are termed monopropellants. Those propellants'involving two materials are termed bipropellants and normally consist ofan oxiv dizer and a fuel. When the fuel component of a bipropellant is spontaneously ignited upon contacting the oxidizer, the fuel is referred to asa hypergolic fuel. Hydrogen peroxide and nitromethane are each well known monopropellants. Well known bipropellants include hydrogen peroxide orliquid oxygenas the oxidizer with ammonia, hydrazine, hydrogen or ethyl 'alcohol-wa'teras the fuel component; and nitric acid as the oxidizer with aniline or furfuryl alcohol as the hypergolic fuel component.

The nitric acidcan either be jwhite fuming nitric acid" or red fuming nitric acid, the latter of which is made where 'R' is a monovalent hydrocarbon radical, R is. selected from a group consisting of hydrogen and monovalent hydrocarbon radicals, R" isa-member of a group consisting of hydrogen, monovalent. hydrocarbon, amino, substituted amino, and phosphondiamido radicals, where, in addition, the N, R,-'and R" radicals together can form one of a fiveand six-membered heterocyclic ring, the R and R" can be the same or different, the number of carbon atoms in'R' does not exceed six and the number of carbon atoms in each of the R and R" radicals does not exceed ten. The hydrocarbon radicals may be cyclic or acyclic, straight or branch-chained, saturated, unsaturated, or aromatic, such as alkyl, aryl, cycloalkyl, alkaryl, aralkyl, alkenyl, cycloalkenyl, ,aralkenyl and alkenylaryl radicals.

Polymers formed by polymerization of phosphonic diamides, where R, ;R' or R" contains one or more aliphatic unsaturated linkages are within the scope of this invention.

Further, according to the invention there are provided polymeric phosphonic diamides which exhibit hypergolic properties when admixed with an oxidizer. Said polymeric phosphonic diamides can be characterized by formulas including the following structural formulas. For example, linear polymers from N,N,N',N-tetramethyl- 1,3-butadiene-l-phosphonic diamide could, if polymerization occurs by 1,4-addition, be represented as having the following type of structure:

If polymerization occurs by 1,2-addition, then the structure could be 4 0:0 ....O--C O=l =C i=0 CHg-NZ N-CHa CHr-N NCH:

CH: CH: CH: H:

It is probable that both 1,2- and 1,4-addition will occur in; the same molecule. Furthermore, in any instance where 1,2-addition occurs, the branching vinyl groups present are loci for further polymerization or cross-linking between polymer chains. 1

If in the above formulas, the methyl groups are re-" placed by allyl groups, further possibilities for polymerization or cross-linking would arise.

Still further according to the invention there is provided a method of using the hypergolic materials of the invention in a bipropellant which comprises the step of admixing said materials with an oxidizer to produce a sudden release of energy.

The phosphonic amides of the invention are hypergolic per se, and are also hypergolic when diluted with'nonhypergolic combustible materials, even in a state of dilution as high as 70 to percent orin some cases higher. Suitable nonhypergolic diluents include hydrocarbon fuels such as'gasoline; toluene, 'various hydrocarbons such as n-heptane, jet fuel and the like. The compounds of the invention can. also be mixed, with-other hypergolic materials suchja srcer't ain organic amines, conjugated-dis olefins, sulfides, and the like. They can be used as sub-;. stantially pure compounds, as isomeric mixtures, or as mixtures of. more than} one phosphonic diamide.

ll lus'trativ'e of the hypergolic organic phosphonic amides of our invention are N ,lI,N ',N '-tfetramethyl-1,3-butadiene-l-phosphonic diamv N,N,N',N'-tetradecyl-'1,3-butadiene-2 phosphonic diamid e, N,'N,N',N'-tetraallyl-l,3-butadiene-l-phosphonic diamide, N,N,N,N'-tetra-2-pentenyl-1,3'-butadiene-2 phosphonic diamide, N,N,N',N-tetrabenz'yl-1,3-cyclohexadiene-1 phosphonic :diamide, N,N,N',N'-tetraocty1-'1,3-cyclohexadiene-Z-phdsphonic di-- amide, a" p J N,N,-N',N' tetraphenylethanephosphonic diamide,

N,N,N,N'-tetracyclohexyl-Z-niethyl l-propene 1 phosphonic diamide, i V i N,N,N',N'-tetra-2-cyclohexenyl-2-methyl-1 propene 2- phosponicdiamide, i i W N,N'diethylbenzenephosphdnic diamide,

N,N dipei'idylethanephosphohic"diamide, 1','3 butadiene-l phosphonic dihydrazi'de [CH ==CHCH=CH-P(O) (NHNH-Q 1,3-butadiene-2-phosphonic dihydrazide, N,N' -ethylenel-butene: l-phosphonie diarnide' N-CH2 o'HaoHioH=e -P(o N,N--ethylene-'1-butene 2-phosphonic diamide, l,3-butadiene-l-phosphonic di(2-phenylhydra 'zide) 1,3-butadiene-2-phosphonic di(2-phenylhydrazide), hydrazobis(1,3-butadiene-1-phophonic hydraz ide) hydrazobis(1,3 butadiene-2 phosphonic hydrazide), N,- N'-1,3-butadiene-l-phosphonylphenylene diamine and N,N'-1,3 butadiene-2-phosphonylphenylenediarnine,

Other suitable phosphonic amides are cyclic compounds;

in" which two phosphorus atoms are linked by two'- h-y- Possible isomers of thesephosphonic amides also come within the scope of this invention, as well as" polymers formed from the phosphonic amides. A presently p'r'e-h ferred group of phosphonic diamides are the phosphonic diamides: and polymers thereof, the method ofp'reparation and composition of which are disclosed and claimed in copending application Serial No. 425,770, filed April 26, 1954, now Patent No. 2,818,406, more especiallyrthe alkapolyene, alkenyne and alkapolyyne phosphonic diamides disclosed and claimed therein; Throughout-the specification and in the claims: the term alkene means a hydrocarbon radical containing at'least one'ethylenic linkage; the term alkapolyenemeans a hydrocarbon-radical containing at least two ethylenic linkages; th'e'term alkenyne means a hydrocarbonradical containing-at least one ethylenic linkage and at least one acetylenic linkage; and the term alkapolyyne means a hydrocarbon radical containing at least two acetylenic linkages. Thus, one example of'an alkapolyne phosphonic diamide is N,N, N-,N-tetramethyl-l,3-butadiene-1-phosphonic diainide. Numerous other examples are given elsewhere herein. Examples of alkenyne phosphonic diamides are N,N,N', N'-tetraallyl-3-buten-l-yne-l-phospho'nic diamide, and N, N,N',N'-tetraa11yl -1-butene-3muted-phosphonic. diamide;

Examples of alkapolyyne phosphonic diamides are N,

N,N,N-tetracy'clohexyl-1,3-pentadiyne-l-phosphonic di ganic phosphonic dihalide at a temperature of to -70 C. withat least four or five molecular equivalents of an amine, the quantity depending on whether dehy drohalogenation'is to take-place simultaneously with the amidation, or not. Suitable phosphonic dihalides for this reaction are 2-chlord-3-butene-l-phosphonic dichloride, 1-chloro-3-butene-2 phosphonic dichloride, 4-chloro-2-butene-l-phosphonic dichloride, 2-chloro-3-cyclohexene-l-phosphonic dichloride,

' l-chloro-3-cyclohexene-2-phosphonic dichloride,-

4-chloro-2 cyclohexene-l-phosphonic dichloride, ethanephosphonic dichloride, l-methyl 2 chloropropane-1-phosphonicdichloride; 2 niethyl=1-chloroprdpane-2-phosphonic dichloride,

benzenephosphonie dichloride andrthe like. Isomeric mixtures of the phosphonic dihalides may be used in the reaction. 1 The phosphonic dihalides used can be'any of thosedisclosed and claimed-in co-pending application Serial No. 425,769, filed April 26, 1954, now Patent No;

- predominates.

2,871,263, which have a hydrogen atom attached to the same carbonatom to which the phosphorus atom is attached. As stated in that application, they are prepared by reacting the corresponding haloalkenephosphorus tetrachloride with acarboxylic acid. Thus, 2-chl0ro 3-bu tenephosphorus tetrachloride, which is'a preferred starting material, is reacted with acetic acidin accordance As stated in the application Serial No. 425,769, filed April26, 1954, now Patent No. 2,871;263, when 1,3-' butadiene is reacted withphosphorus pentachloride to; form a chlorobutenephosphorus tetrachloride three possible isomers can be obtained, i'.e.,

At present it is believed that isomer No. 1, above, When a mixture of the said isomers is reacted with a carboxylic acid according to the above given equation a mixture of'the corresponding chlorobutenepho'sphonic dichlorides is obtained. Thus, when a mixture of the said chlorobutenephosphonic dichlorides' is u'sed-as'a starting. material in the reaction with an u'n saturated a'n'iine'sucha's diallyla'rnine the'corre'spondin'g N,N,N',N tetraallyl-1-3-butadiene-1-phosphonle diamlde When vinyl acetylene is reacted with phosphorus pentachloride to form a chldrobutadienephosphorus tetrachloride one of the isomers which can be obtained has the following structure:

When this isomer is reacted with a carboxylic acid according to the above given equation the corresponding chlorobutadienephosphonic dichloride is obtained. Thus, when the said chlorobutadienephosphonic dichloride is used as a starting material in the reaction with an unsaturated amine such as diallylamine Z -chIor I S-butadiene-l-phosphonic .diamide will be obtained. By dehydrohalogenation with a strong base such as potassium hydroxide the corresponding alkenynephosphonic diamide is obtained, i.e.,

The amines which can be used in this preparative method can be primary or secondary .aro'matic or secondary aliphatic, carbocyclic, or heterocyclic monoamines or polyamines... Hydrazine anditsderivatives are also applicable;' Illustrativeof such amines or hydrazines are.

6 phosphonic amide formed is capable of undergoing additron polymerization'to yield linear polymericphosphonic amides whichalso are hypergolic. For example, the

. -phosphonic amide formed from the isomeric ChlOl'Obl-l'.

idation catalysts. These oxidation catalysts include certain metal salts such as the chlorides and naphthenates of iron, zinc, cobalt and similar heavy metals.

dimet ylamine, diallylamine, dibenzylamine, diphenyl-y amine, dicyclohexylamine, aniline, piperidine, hydrazine, N,N-dimethylethylenediamine, phenylhydrazine, o-phenylenediamine, N-methylaniline and the like. When the amine used is a polyamine,.the reaction can proceed through multiple condensation reactions to yield a crosslinked polymer. N,N"-dirnethylethylenediamine, for example, forms a polymer which can be represented by the 1 ,51: 5 L1,. H. ml.

It is generally accepted that in order to form The following examples are tidn. EXAMPLE I .The unsaturated organic phosphonic diamides listed "below were'tested for spontaneous ignition, employing both'whit'e fuming'nitric' acid (WFNA) and red fuming nitric acid (RFNA) as the oxidizer. In each test, 0.13

ml. of a mixture of isomeric phosphonic diamides with varying percentages'df pure grade n-heptane or toluene ,was dropped into'a 1""x"8" *test tube containing 0.3

ml. of either white or red fuming nitric acid.& The

mixture of the organic phos'phonic diamides and hydroillustrative of the invencarbon, upon coming into contact with the fuming nitric acid, ignited spontaneously. Normal heptane was employed as'a diluent todetermine the maximum amount of dilution that the'phosphonic diamides could tolerate and still retain the property of being'hypergolic. When the hyper'gol was not soluble in n-heptane, toluene was used as the diluent. Tests were conducted at room temperature, i.e., about 70 F., and at -40 F. In Table 1 below are given the maximum dilutions at which the phosphonic diamides retained their self-ignition properties.

' EXAMPLE II t The organic phosphonic diamides tabulatedbelow wereas the time interval between contact of the oxidizer with the fuel and the beginning of sustained combustion. Long ignition delaysare undesirable, as they may be the cause ofhard starts, rough burning, and frequently, destructive. explosions. In Table 2 is given a summary of ignition delay data obtained in the drop'test apparatus,.-using white fuming nitric acid as the oxidant. The drop test apparatus comprises an injection nozzle activated by a solenoid coil which is used to inject acid into a small quantity of fuel contained in the bottom of a test tube. The ignition delay interval is taken as the time between contact of the acid and fuel and the presence of flame as sensedby a photocell. The values were obtained by averaging at least six runs on each fuel.

Table 1 Maximum Percent Maximum Percentage Dilution with age Dilution with Toluene n-Heptane Material Room Temperature Room Temperature 40 F.

Rrr u WFNA RFNA WFNA RFNA WFNA Isomeric N,N,N',N'-tetramethyl-1,3-butadtenephosphonic diamides 70 60 50 Isomerlc N,N,N',N'-tetraal1yl-1,3-butadtenephosphonic diamides .,50 60 Isomerie N'.N,N',N-tetraallyl-1.3-butadienephosphonic diamides (crude reaction mixture) 80 70 60 60 Table '2;

SUMMARY OF IGNITION DELAY DA'IA WITH WHITE FUMING NITRIC ACID Drop Test Apparatus Average Average Average Average Ignition Deviation, Percent Ignition Deviation, Percent Delay, Mllllsec. Deviation Delay, Milllsee. Deviation M ilu Mlllisee Isomerlc N,N,N,N-tetraallyl-l,

3-butadienephosphon'lc dlamides 33 2. 9 8. 8 925 308. 4' 33. 3 Isomerlc N ,N,N ,N'-tetramethyl- 1,3-butadienephosphonic diamides 44 3.8 8.6 Isomerlc N ,N.N',N-tetramethyl- 1,3-butadienephosphonle diam ides 17 2. 6' 15. 3 341 171. 6 60. 4 Isomerlc N,N,N,N'-tetramethyl- 1,3-butadienephosphonlc diamldes+10% toluene 34 1. 8 5. 3 Isomerie N,N,N, N-tetramethyl- 1,3-butadlenephosphonic dlam-' ldes+% toluene 43 1.8 4.2

EXAMPLE III The isomeric N,N,N',N-tetraally1-1,3-butadienephos-,- phonic diamides were prepared by the following pro-- cedure:

To a solutionot 107 g. (1.1,mol) of anhydrous di-;

allylamine in 100 m1. of anhydrous ether, cooled to about -50 F., was added dropwise, with constant stirring, 41.5 g. (0.2 mol) of the 'chlorobutenephosphonic dichloride, the preparation of which is described and claimed in copending application Serial No. 425,769, filed April 26, 1954, now Patent No. 2,871,263. When all of the phosphonic dichloride had been added, the flask was warmed gently to room temperature, and the reactionwas allowed to proceed with intermittent cooling to keep the temperature below 40 C., until, after about one hour, cessation of heat evolution indicated that the reaction had proceeded substantially to completion. The precipitate of amine hydrochloride was removed by filtration, washed with ether, and{dried. The ether was removed from the filtrate by} distillation,

and 100 ml. of n-pentane wasadded to*precipitatethe remaining amine hydrochloride, which was removed by filtration. The combined weights of the aminehydrochloride indicated a 98.5 percent yield of the theoretical total yield. Pentane and excess amine were stripped from the filtrate by distillation in vacuo, and the residue was distilled to yield N,N,N,N-tetraallyl-l,3-butadiene-' phosphonic diamide, boiling at 157 to 170 C. at 1mm. of Hg. Polymer formation occurred in the flask.

A sample prepared by a' procedure similar to the one described above gave the following analysisi Calculated for C H PON Q: C, 65.7; H, 8.6; P, 10.6. Found: C, 63.2; H, 8.9; P, 10.3.

EXAMPLE IV The isomeric N,N,N,N' tetramethy1-- 1,3.- butadienephosphonic diarnides were prepared by the following properature, and the excess dimethylaminewas driven'ofi' After adding 50 cc. of ether, theby gentle heating.

phosphonic diamide, boiling.at 102-120 C. at l.25-2.5 mm. The residue remaining in the distillation flask was a clear, amber resin.

EXAMPLE V A second run was.v made for the purpose of preparing additional isomeric N,N,N,N'-tetra'methyl-1,3 butadienephosphonic diamides. 100 g. (2.22 mol) of anhydrous dimethylamine was placed in a 500 cc. S-necked flask, equipped with stirring unit, dropping funnel, and ther mometer.

dichloride which was prepared according to the procedure described in Example II of co-pending' application,

Serial No. 425,769, filed April 26, 1954, now Patent" During this addition the temperature oil, was stripped of ether, andthen distilled under: re-

amine hydrochloride was removed by filtrationi a'n'd' washed with cc. of ether.

46g. of dirnethylamine;

from the filtrateand the residue wasdistilled in vacuoreduced pressure. I like oil remained. When it was attempted to distill 61.1 g. of this'cru'de product at reduced pressure, 14.89 of duced pressure. 20.7 g. of a fraction boiling at 116- 118 at 0.9 to 1.2 mm. Hg was obtained. This represents a theoretical yield of 53.7%. Its refractive index was N 1.5023.

EXAMPLE VI A 500 cc; flask equipped with dropping funnel, stirring unit, and reflux condenser was placed in a Dry Iceacetone bath. 107 g. (1.1 mols) of distilled diallylamine was agitated-in the flask. Into this was dropped slowly, 41.5 g. (0.20 mol) of chlorobutenephosphonic dichloride (prepared as described in Example I of co-pending application, Serial No. 425,769, filed April 26, 1954) dissolved in 100 cc. of ether. The reaction was exothermic with ready separation of the amine hydrochloride. 50 co. more of ether was added and the mass filtered. The filtrate and 500 cc. of ether washings were combined. A taint cloud of precipitate settled slowly. The diallylamine hydrochloride was dried for 3 hours at C. and then weighed. 72.9 g. were obtained, a 91% theoretical yield. The filtrate was stripped to 50 C. under 62.2 g. of a red, very viscous, jellydiallylamineand 2.5 g; of a liquid boiling at 25 C. at 045mm. Hg were obtained as overhead while polymerto-yicld 21.5 g; ofN;N;N,Ntetramethyl-1;3-butadiene-- 7giZation-occurredinthe flask to yield 43.3 g. of a dark It wascooled to -70 C. by meansof'a Dry Ice-acetone bath, and then into it was dropped slowly 42.5 g. (0.205 mol) of chlorobutenephosphonic' 9 plastic solid. The crude product, the distilled product, and the polymer were all hypergolic with white fuming nitric acid and red fuming nitric acid.

Not all nitrogen containing compounds are hypergolic. The following tabulation illustrates results obtained when testing the listed compounds for hypergolicity in accordance with the method given in Example 1.

where R is a monovalent hydrocarbon radical, R is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals, R" is selected from the group consisting of hydrogen, monovalent hydrocarbon, amino, phenyl substituted amino, and phosphondiamido radicals, where, the R and R" can be different, the number of carbon atoms in R does not exceed six and the 'NI=no ignition.

While certain polymers have been represented herein by structural formulas it should be understood that all stages of polymerization, i.e., from substantially unpolymerized to substantially completely polymerized, of the compounds of the invention are within the scope of the invention.

Although there is no reason to suspect that the structural formulas'given as representing the materials of the invention are incorrect, since said formulas were developed according to standard methods well known to those skilled in the art, the invention is not to be unduly limited by said formulas.

In the specification and in the appended claims the term bipropellantmeans a material of the invention plus an oxidizer, in which spontaneous combustion takes place to provide a sudden release of energy as a result of contact of said material and said oxidizer; .hypergolic or hypergolicity is the property of a material characterized by spontaneous ignition to provide a sudden release of energy when the material is contacted with an oxidizer and an oxidizer is a material which causes spontaneous ignition of the compounds of the invention upon contact therewith.

Reasonable variation and modification are possible within the scope of the foregoing disclosure and the appended claims to the invention the essence of which is that phosphonic diamides and/or polymeric phosphonic diamides are hypergolic when admixed with an oxidizer.

We claim:

1. A method for imparting immediate thrust to a mass, comprising introducing separate streams of an oxidizer component and a fuel component into contact with each other in a combustion chamber of a reaction motor in such proportion as to produce spontaneous ignition, said fuel component being selected from the group consisting of a phosphonic diamide and a polymer of said diamide, wherein said diamide is characterized by the structural formula o N(R)(R" 2-phosphonic diamide.

5. A method according to claim l'wherein said phosphonic diamide is N,N,N',N-tetraallyl-l 3-butadiene-lphosphonic. diamide.-

6. A method according to claim 1 wherein said phosphonic diamide is N,N,N',N-tetraallyl-1-3-butadiene-2- phosphonic diamide.

7. A method according to claim 1 wherein said phosphonic diamide is a mixture of isomeric N,N,N',N'- tetraallyl-l-3-butadienephosphonic diamides.

8. A method according to claim 1 wherein said phosphonic diamide is a polymeric N,N,N,N'-tetraallyl-l-3- butadienephosphonic diamide.

9. A method according to claim 1 wherein said phosphonic diarnide is a polymeric N,N,N',N-tetramethyl- I-B-butadienephosphonic diamide.

10. A method according to claim 1 wherein said oxidizer is selected from the group consisting of white fuming nitric acid, red fuming nitric acid, hydrogen peroxide, liquid oxygen, liquid ozone, and mixtures of nitric and sulfuric acids.

11. A method according to claim 1 wherein said phosphonic diamide is dissolved in a non-hypergolic combustible material selected from the group consisting of toluene, n-heptane, gasoline and liquid hydrocarbon jet fuel.

References Cited in the file of this patent UNITED STATES PATENTS 2,382,309 Hamilton Aug. 14, 1945 

1. A METHOD FOR IMPARTING IMMEDIATE THRUST TO A MASS, COMPRISING INTRODUCING SEPARATE STREAMS OF AN OXIDIZER COMPONENT AND A FUEL COMPONENT INTO CONTACT WITH EACH OTHER IN A COMBUSTION CHAMBER OF A REACTION MOTOR IN SUCH PORPORTION AS TO PRODUCE SPONTANEOUS IGNITION, SAID FUEL COMPONENT BEING SELECTED FROM THE GROUP CONSISTING OF A PHOSPHONIC DIAMIDE AND A POLYMER OF SAID DIAMIDE, WHEREIN SAID DIAMIDE IS CHARACTERIZED BY THE STRUCTURAL FORMULA 